Tiltable chair construction



I Dec. l'1, i970 H, ANDERss'N Y TILTABLE CHAIRr CONSTRUCTION l 2 sheets-sheet' 1 Filed nay io, 196e 'lllllll c. l, 1,970 H. Auml-:Rssojw` I TILTABLE CHAIR CONSTRUCTION A Filed May l1o, 1968 2 Sheets-Sheet 2 INVENTORS', H Ease 2T AN mi: 255cm ATTORNEYS United States Patent O 3,544,159 TILTABLE CHAIR CONSTRUCTION Herbert Andersson, Dalum, Sweden, assignor, by mesne assignments, to Consolidated Burris International, Ltd., Lincolnton, N.C., a corporation of North Carolina Filed May 10, 1968, Ser. No. 728,187 Int. Cl. A47c 3/18 U.S. Cl. 297-303 Claims ABSTRACT OF THE DISCLOSURE A supporting structure for a tiltable chair seat in which a frame secured to the seat bottom has laterally spaced depending post means thereon in which opposite end portions of a torsion bar are secured for resiliently resisting tilting movement of the chair seat. A shaft is penetrated by a medial portion of the torsion bar, and the shaft is adapted to be mounted in an upright position in a mating bore in a chair base or pedestal, preferably for swivel movement therein.

This invention relates to tiltable chairs and more particularly to an improved structure utilizing a torsion bar for supporting a chair seat for tilting or rocking motion upon a chair base or pedestal.

Various forms of chair seat supporting structures have been proposed heretofore in which torsion bars have been employed to permit rocking or tilting the chair seat while torsionally resisting such tilting. The prior art forms of supporting structures have had various disadvantages in that they have included many intricate parts of expensive manufacture, such parts have been large, cumbersome and relatively heavy, thereby adding undesirably excessive weight to the chair construction, and/or they have been of unsightly construction detracting from what might have been an otherwise aesthetic appearance to the chair.

It is an object of this invention to provide an improved supporting structure for a tiltable chair seat which structure is of simple, relatively lightweight and compact construction, includes relatively few parts, and will not impart an undesirable appearance to the chair, and wherein the supporting structure includes a torsion bar which tends to maintain the chair seat in a generally horizontal position, but is bendable to permit tilting the chair seat while torsionallly resisting such tilting.

It is a more specific object to provide a chair seat supporting structure including a frame adapted for securement to the bottom of the chair seat and having a pair of laterally spaced depending post means thereon in which opposite ends of a torsion bar are secured, and wherein a shaft is penetrated by a medial portion of the torsion bar. The shaft is adapted to t in a vertical bore in a chair base or pedestal with the torsion bar supported by the chair base so that the torsion bar supports the chair seat and permits tilting or rocking of the chair seat relative to the shaft and the chair base while torsionally resisting such tilting or rocking.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings, in which:

FIG. 1 is a side elevation of a tiltable chair construction providing one embodiment of chair seat supporting structure according to this invention;

FIG. 2 is an enlarged fragmentary vertical sectional View looking rearwardly substantially along line 2-2 in FIG. l;

FIG. 3 is an enlarged fragmentary vertical sectional view similar to the lower central portion of FIG. 2 and showing an improved means for retaining the upright Patented Dec. l, 1970 shaft of the instant supporting structure in the vertically extending bore of the chair base or pedestal;

FIG. 3A is a sectional view of the retaining cap of FIG. 3 removed from the shaft;

FIGS. 4 and 5 are fragmentary vertical sectional views taken substantially along lines 4-4 and 5-5 in FIG. 2;

FIG. 6 is a perspective view looking upwardly at the improved supporting structure shown in FIGS. 1-5, but showing the upright shaft thereof removed from the chair base;

F IG. 7 is a view similar to FIG. 6, but showinga `second embodiment of the chair seat supporting structure of the instant invention;

FIG. 8 is an enlarged fragmentary Vertical sectional view taken substantially along line 8-8 in FIG. 7; and

IFIG. 9 is an enlarged fragmentary sectional plan view taken substantially along line 9-9 in FIG. 7.

Referring more specifically to the drawings, a tiltable swivel chair comprising a chair seat 10 and a chair base or pedestal 11 is shown in FIG. 1 provided with one embodiment of the improved chair seat supporting structure of this invention which is broadly designated at 12. Chair base 11 may be of conventional or other construction and, as shown, chair base 11 includes an upstanding central body 13 having a substantially vertically extending bore or cavity 14 therethrough. Leg members 15 are suitably connected to and extend substantially radially from body 13, and suitable foot members 16 may be secured to the outer lower end portions of leg members 15. If desired, a tubular bushing 20 may be pressed into bore 14, with a radial flange 2|1 on the upper end of bushing 20 bearing against the upper surface of body 13. Bushing 20 may be made from any suitable bearing material, such as plastic, brass, etc.

The chair seat supporting structure 12 comprises a frame which preferably is in the form of a relatively thin substantially rectangular base plate member 23 adapted to be secured in a generally horizontal position to the bottom of chair seat 11, as by means of screws 24 (FIG 2). Connected to opposed end portions of plate member 23, and depending therefrom, is a pair of suitable post means 25, 26 which are laterally spaced apart from each other with respect to chair seat 10. Post means 25, 26 may be formed integral with plate member 23 or they may be fixedly secured to plate member 23. As shown in FIGS. 2, 4, 5 and 6, post means 25, 26 are welded to the lower surface of plate member 23.

In the first embodiment of the invention, each post means 25, 2.6 is shown in the form of a pair of blocks so that, in effect, the post means 25, 26 are bifurcated to provide aligned slots 27 therethrough for receiving therein opposite end portions of a horizontally disposed, elongate, relatively thin metallic torsion bar 30. Torsion bar 30 extends horizontally with its widthwise dimension extending vertically; i.e., with its widthwise dimension extending substantially perpendicular to the upper surface of plate member 23 and substantially parallel to the axis of a shaft or spindle 35, as will be later described.

The width of slots 27 in post means 25, 26 should be such as to maintain torsion bar 30 with its widthwise dimension in substantially perpendicular relation to plate member 23 and also to minimize relative movement between torsion bar 30 and post means 25, 26 when torsion bar 30 is subjected to a longitudinally bending or twisting force, as will be later explained, so as to avoid producing squeaking sounds by the torsion bar 30v rubbing against the walls of slots 27.

As a further precaution against producing such squeaking sounds, a cushon member 31 is positioned between each side of torsion bar 30 and the corresponding wall of each slot 27. Cushion members 31 may be made from rubber or any other suitable resilient material. As shown, the two cushion members 31 adjacent each end of torsion bar 30 may be formed collectively of substantiallyr U- shaped one-piece construction (-PIGS. 5 and 6). Opposed ends of torsion bar 30 may be further rigidly secured in the desired position, spaced below plate member 23, by means of screws 32. As shown, one of the screws 32 penetrates one block of the corresponding post means 25 or 26, as the case may be, and also loosely penetrates the two corresponding cushion members 31 and the corresponding end portion of torsion bar 30, but the corresponding screw is threaded into the other block of the corresponding post means. Thus, the two blocks of each post means clampingly secure opposite ends of torsion bar 30 in fixed relation to plate member 23 and in spaced relation below plate member 23. It is believed that cushion members 31 serve an additional useful function in that the bending stresses applied to torsion bar 30 appear to be effective over the full length of the torsion bar as opposed to only that portion of its length between the post means 25, 26.

A medial portion of torsion bar 30 extends through the slotted or bifurcated upperend portion of the shaft or spindle -35 whose transverse slot is indicated at 36 and is of such width thatopposite sidewalls thereof firmly engage opposite side surfaces of torsion bar 30. Shaft 35 may be of tubular form and is of such diameter as to lit in the body 13 of chair base 11;,i.e., within flanged bushing 20, so that the supporting structure 12 and chair seat may be swiveled or rotated relative to chair base 11. A metallic washer 37 (FIGS. 2 and 4) may be provided on shaft 35`and positioned between` the lower surface of torsion bar 30 and' the upper surface of bushing flange 21 for supporting the torsion bar 30, the post means 25, 26, the base plate member 23, and the chair seat 10 upon the tubular body 13 of chair base k11.

From the foregoing description, it is apparent that the torsion bar normally maintains chair seat 10 in a substantially horizontal or slightly tilted position, and that the chair seat 10 may be rocked or tilted relative to shaft 35, during which theopposite end portions of torsion bar 30 move rwith the post means 25, 26 while the medial portiton of torsion bar 30 remains with its widthwise dimension occupyinga substantially vertical position in the upper portion of shaft 35. Thus, torsion bar 30 is twisted during the tilting of the chair seat 10 while it resists such tilting motion and tends to return the chair seat to the normal position. If so desired, plate member 23 may be positioned at a slight angle of about 8 out of right angular relation to shaft 35 so that the chair seat may normally occupy a slightly backward tilted position as shown in FIG. 1 while torsion bar 30 is in relaxed condition.

Novel means are provided for limiting the extent to which the chair seat 10 may be titled out of its normal substantially horizontal position. To thisend, it will be observed in FIGS. l3 and 6 that the slotted upper end of shaft 35 extends a relatively short distance upwardly above the upper edge of torsion bar 30 and has a transverse tilt-limiting bar 40 fixed thereon, as by welding. Bar 40 is spaced below plate member 23 4and its medial porl tion is threadedly penetrated by a set screw 41 whose lower end bears against the upper edge of torsion bar 30 for maintaining the lower edge of torsion bar 30 in engagement with the bottom of the slot 36 through shaft 35. Plate member '23 may be have an opening 42 therethrough to facilitate access to screw 41 and to reduce the desired adjusted position by means of a lock nut 45. Thus, resilient cap 43 may be adjusted relative to tilt-limiting bar 40 such as to permit a relatively small extent of forward tilting motion of chair seat 10, if desired, it being noted that the abutment or cap 43' is disposed in close proximity to the front lower surface portion of plate member 23 in FIG. 4.

It is apparent that the rear end portion of tilt-limiting member 40 is normally spaced a substantial distance below the rearmost portion of plate 23 as compared to the relationship between abutment 43 and the plate member 23, thus permitting substantial rearward tilting motion to be imparted to chair seat 10 before the rear portion of plate member 23 may engage tilt-limiting bar 40. A suitable cushion member 47, which may be made from rubber or any other suitable resilient material, may be mounted on the rear portion of tilt-limiting bar 40 for cushioning the'movement of plate member 23 toward tilt-limiting bar 40 and also for preventing the occurrence of an undesirable sound upon impact of plate member 23 with tilt-limiting bar 40.

VIt will be observed in FIGS. 2 and 3 that the lower end of shaft 35 terminates adjacent the lower end of tubular body 13 of chair base 11. It is desirable that the lower end of post member 35 does not Vprotrude below the lower end of tubular body 13 for the sake of good appearance. Moreover, the lower end of body 13 may be located so close to the oor upon which the chair base rests that only a short protruding length of post member 35, if any, could be accommodated below body 13. Thus, it has been customary heretofore to retain an upright shaft or spindle in the tubular body 13 by inserting a metal snap ring or ilexible split collar in a peripheral groove in the lower portion of the spindle so that such snap ring could engage the lower end of the bushing 20 and thereby restrain the pOst member from being lifted out of the chair base. It is apparent that the insertion of such a metal snap ring or ilexible split collar in a peripheral groove of a shaft housed within the tubular body 13 is quite dilicult and has required special tools, since the lower portion of the shaft 25 is practically inaccessible.

Accordingly, novel means is provided, as shown in FIGS. 2, 3 and 3A, for retaining shaft 35 in tubular body 13. To accommodate the novel shaftretaining means, the lower end of bushing 20 is spaced a substantial distance above the lower extremity of tubular body 13, and the lower portion of shaft 35, below the lower end of bushing Z0, is provided with a peripheral groove 50 therein defining, at the lower extremity of shaft 35, an annular shoulder 51. The shaft retaining means comprises a retaining cap, broadly designated at 53, including a deformable exible wall 54 of an elastic synthetic plastic material. In its relaxed state, the inner surface of annular wall 54 may be of substantially uniform diameter throughout its length and may be of from about .010 to .030 inch lesser diameter than the external diameter of shoulder 51 so that the annular wall 54 of retaining cap 53 is stretched and enlarged as it is manually forced over shoulder 51, but as the annular wall is being forced beyond the shoulder 51, it tends to resume its original internal diameter, thus entering the annular groove 50 and locking retaining cap 53 on the lower end portion of shaft 35.

It is apparent that the external diameter of annular wall 54 should be substantially less than the internal diameter of the bore 14 of tubular member 13. The lower portion of annular wall 54 is provided with a radially outwardly projecting flange 55 which seats against the lower end of' tubular body 13 when the annular wall 54 is properly installed on the lower end portion of shaft 35.

The inherent elasticity of annular `wall 54, and the relationship of its internal diameter to the external diameter of shoulder 51 should be sufficient to ensure that shaft 35 will not be pulled out of tubular body 13 when the chair is lifted to move the same from place to place. On the other hand, it is to be understood that the elastic nature of annular wall 54 of retaining cap 53 may be such that cap member 53 may be removed from the lower end portion of shaft 35 by inserting the end of a screw driver or other suitable implement between flange 55 and the lower end of tubular body 13, if desired. To facilitate installation of cap member 53 on the lower end of shaft 35 in the manner hereinbefore described, the lower outer peripheral edge of shoulder 51 may be rounded or beveled, as desired. To lend rigidity to the lower portion of cap 53, ange S may be in the form of a disc which entirely closes the bottom of annular wall 54. Also, it is preferred that flange or disc 55 is formed of the same material as and is integral with the annular wall 54.

The second embodiment of the chair seat supporting structure shown in FIGS. 7, 8 and 9 is quite similar to the rst embodiment, with the exception of the form of post means in which opposite ends of the torsion bar are mounted, and with the exception that the frame or base plate member is shown extending at right angles to the shaft 35. Therefore, the parts shown in FIGS. 7, 8 and 9 will bear the same reference characters as similar parts shown in FIGS. 1-6, where applicable, with the prime notation added, to avoid repetitive description.

Although plate member 23 extends downwardly and rearwardly at a shallow angle in FIGS. 1, 4 and 5 relative to shaft 35, it is apparent that it may extend perpendicular or at a right angle with respect to shaft 35. Also, although plate member 23 is shown in FIG. 8 extending perpendicular or at a right angle to the shaft 35', it is apparent that plate member 23' also may extend'downwardly and rearwardly at an angle in a manner similar to that at which plate member 23 is shown in FIG. 5, if desired.

As shown in FIGS. 7, 8 and 9, each-post means 25', 26 may be of tubular form and the transverse slots 27 therethrough are shown as being of about the same depth as the width of torsion bar 30. Thus, post means 25', 26' may retain torsion bar 30 in the desired spaced relation below plate member 23 without relying solely upon the screws 32 or the clamping effect produced by tightening screws 32 in post means 25', 26'. Cushion members such as are indicated at 31 in FIGS. 2, 5 and 6 are not used in the second embodiment of the invention, but may be used, if desired.

It is thus seen that I have provided an improved supporting structure for mounting a tiltable chair seat on a chair base, wherein the torsion bar extends through and is substantially axially aligned with the spindle with its opposite ends being secured within post means carried by a plate member secured to the bottom of the chair seat, thus providing a simple, compact, easily assembled and economical unit which will not detract from the desired aesthetic appearance of the chair.

In the drawings and specification there have been set forth preferred embodiments of the invention and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.

What is claimed is:

1. A supporting structure for tiltably mounting a chair seat on a pedestal having a vertically extending shaftreceiving cavity therein; said supporting structure comprising a frame adapted for securement to the bottom of the chair seat and having a pair of laterally spaced post means fixedly connected thereto and depending therefrom, a shaft adapted for insertion into the shaft-receiving cavity of the pedestal, an elongate horizontally disposed torsion bar having opposite ends thereof extending substantially through and secured to said pair of post means, said torsion bar also having a medial portion thereof penetrating said shaft and restrained from turning movement therein, said torsion bar being bendable about its longitudinal axis relative to said post means and said shaft, by tilting said frame relative to said shaft, while torsionally resisting such tilting, and means for limiting the extent to which said frame may be tilted relative to said shaft.

seat on a pedestal having a vertically extending shaftreceiving cavity therein; said supporting structure comprising a pair of post means, base means for rigidly securing said post means in ixed laterally spaced relationship to the bottom of the chair seat, a shaft adapted for insertion into the shaft-receiving cavity of the pedestal, a horizontally disposed, elongate, relatively thin metallic torsion bar having opposite end portions thereof extending substantially through said pair of post means and being secured to said post means, a medial portion of said torsion bar penetrating and secured to said shaft with the widthwise dimension of said torsion bar extending substantially parallel to said shaft, and said torsion bar being adapted to bend about its longitudinal axis relative to said post means and said shaft, by tilting said post means relative to said shaft, while torsionally resisting such tilting.

3. A structure according to claim 2, in which said base means comprises a plate member to which said post means are attached, wherein the upper edge of said torsion bar is spaced below said plate member, and means limiting the extent to which said post means may be tilted, said limiting means comprising a second bar connected in fixed relation to the upper end of said shaft and extending over and transversely of said torsion bar, said second bar normally being spaced below and out of engagement with said plate member, and a resilient covering means on at least one end of said second bar being engagea-ble by said plate member upon predetermined tilting of said post means and said plate member relative to said shaft.

4. A structure according to claim 3, including abutment means carried by the other end of said second bar and also being engageable by said plate member when said plate member occupies a normal substantially horizontal position.

5. A structure according to claim 4, wherein said abutment means comprises an element vertically adjustable relative to said second bar and having a resilient member on its upper end for engaging said plate member.

, 6. A structure according to claim 3, in which said shaft is fixed to said torsion bar by means of a set screw threaded through said second bar and engaging the upper surface of said torsion bar.

7. A structure according to claim 2, including a thin resilient pad between each side of said torsion bar and the respective post means for cushioning the mounting of said torsion bar in said post means.

8. A structure according to claim 2, in which said post means are each provided with a slot through which a corresponding end portion of said torsion bar extends, and a cushion member of resilient material positioned between each side of said bar and the corresponding wall defining each slot.

9. A supporting structure for tiltably mounting a chair seat on a pedestal having a vertically extending post-receiving bore therethrough; said supporting structure comprising a frame adapted for securement to the bottom of said chair seat and being provided with a pair of laterally spaced depending post means thereon, an elongate, horizontally disposed, torsion bar having opposite end portions thereof secured to said post means, a shaft of circular cross-section having its upper end penetrated by and secured to a medial portion of said torsion bar and adapted to lit in said bore for rotational movement therein, said shaft having a peripheral groove therein spaced from its lower end and defining an annular shoulder adjacent the lower end of said post, a retaining cap having an elastic annular wall adapted to snugly engage said shoulder and the bottom of said annular groove, and said retaining cap having a flange thereon adapted to engage the lower surface ofsaid pedestal adjacent said bore when said annular wall is in engagement with said shoulder and the bottom of said annular groove to prevent said shaft from being pulled out of said bore when a lifting force is applied to said chair seat.

10. In a chair construction including a chair base having a substantially vertically extending shaft-receiving bore therethrough, a chair seat, and a supporting structure for the chair seat including a substantially vertically disposed shaft positioned for rotary movement in said shaft-receiving bore, said shaft terminating at its lower end within said bore and having an annular shoulder on its lower end; the combination therewith of means for securing said shaft against axial upward movement in said bore and comprising a retaining cap having an annular wall of elastic synthetic material, said annularwall having an internal diameter which is less than the diameter of said shoulder when the annular wall is in relaxed condition, said annular wall being positioned around and stretched by said shoulder on said shaft and extending upwardly beyond said shoulder whereby said annular wall gripping- References Cited UNITED STATES PATENTS 15 BOBBY R. GAY, Primary Examiner G. O. FINCH, Assistant Examiner U.S. Cl. X.R. 

